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Forensic Serology. Chapter 8. Blood Components. Plasma--fluid part of blood unclotted blood Erythrocytes—hold hemoglobin and transport oxygen Leukocytes—immune cells Platelets--clotting

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blood components
Blood Components
  • Plasma--fluid part of blood unclotted blood
  • Erythrocytes—hold hemoglobin and transport oxygen
  • Leukocytes—immune cells
  • Platelets--clotting
  • Serum—yellow fluid that remains after clotting of blood, mostly water + dissolved substances (proteins, ions, etc)
antigen and antibodies
Antigen and Antibodies
  • Blood Type A has A antigens and B antibodies
  • Blood Type B has B antigens and A antibodies
  • Blood Type AB has both A and B antigens and no antibodies
  • Blood Type O does not have any antigens but both A and B antibodies
  • Positive blood has Rh(D) antigens = Rh+
  • Negative blood does not have Rh(D) antigens but has D antibodies = Rh-
  • Positive blood will agglutinate with Anti D serum
  • Negative blood will not agglutinate with Anti D serum
  • A blood will agglutinate with Anti A serum
  • B blood will agglutinate with Anti B serum
  • AB blood will agglutinate with both anti A and anti B serum
  • O blood will not agglutinate with anti A or anti B
paternity testing with blood type
Paternity Testing with Blood Type
  • A Blood Type—AA or AO
  • B Blood Type—BB or BO
  • O Blood Type—OO
  • AB Blood Type—AB
  • Parent gives each offspring one of two alleles
immunoassay techniques
Immunoassay techniques
  • Used to detect drugs in blood and urine
  • Animals are injected with proteins with drug antigens—animal makes drug detecting antibodies that can be harvested
  • Presumptive drug testing with these cultured antibodies can be used to detect opiates, cannabinoids, cocaine, amphetamines, phencyclidine, barbituates and methodone
producing antibodies
Producing Antibodies
  • Radioimmunoassay (RIA)—uses radioactive tags to find drugs
  • Enzyme-Multiplied Immunoassay Technique (EMIT)—fast and used with urine; adds antibodies to urine that bind to specific drugs
  • Polyclonal and Monoclonal Antibodies—animals produce many different antibodies when exposed is polyclonal; scientists need one kind of antibody (monoclonal; fused with cancer cell to make hybridoma cell
blood stain analysis
Blood Stain Analysis
  • 3 Questions
    • Is it blood?
    • Is it human?
    • Can it be matched closely to a particular person?
presumptive color testing
Presumptive Color Testing
  • Benzadine color test—use has been reduced because it is a carcinogen; measures for presence of hemoglobin
  • Kastle-Mayer—uses phenolphthalein as an indicator, and hydrogen peroxide to cause the conversion of catalase to give pink color; will test positive with samples with catalase (animal and some plant material)
  • Presumptive blood test
  • Reaction with blood emits light that can be seen in darkened area
  • Sprayed on area, turn dark, emits blue light
microcrystalline tests
Microcrystalline Tests
  • Takayama test
  • Teichmann tests
  • Add chemicals to blood that causes hemoglobin-containing crystals to form
  • Susceptible to contaminants and less sensitive that color tests
precipitin test
Precipitin Test
  • Used to determine if blood stain is human or from animal
  • Grow antibodies to human blood in rabbit; use antibodies to test for presence of human antigens; Human antiserum
  • Rabbits can be used to make antibodies against various animal bloods as well
gel diffusion
Gel Diffusion
  • Use agar gel—antibodies and antigens come together in medium plate
  • Blood and human antiserum are loaded into wells
  • Precipitant forms if blood is human between two wells
blood spatter
Blood Spatter
  • Important Blood Qualities to Interpret Blood Spatter
    • Surface texture—more spatter with softer, porous material
    • Direction of travel—pointed end faces direction of travel
    • Impact angle—right angle yields circular stain
    • Origin of spatter—draw lines through many spatter points; point of intersection is origin of spatter
forensic analysis of semen
Forensic Analysis of Semen
  • Tests for Presence of Semen
    • Acid Phosphatase Stain—acid phosphatase is made by the prostate gland and added to semen during ejaculation; presence can be detected by acidic sodium alpha napthylphosphate and fast blue dye or 4-methyl umbelliferyl phosphate (will fluoresce)
    • Microscopic examination—look for presence of sperm cells
    • Prostate specific antigen—polyclonal antibodies grown in rabbits used to bind to p30 protein or prostate specific antigen
rape evidence collection
Rape Evidence Collection
  • Rape Kit Collection from victims
    • Hair samples: head, pubic, body
    • Body opening swabs: vagina, anus, mouth
    • Blood sample
    • Fingernail scrapings
    • All clothing
    • Urine sample
  • Collected from male suspects
    • All clothing
    • Hair: head, pubic, and body
    • Genital swab
    • Blood sample
    • Cheek cells